I am not 100% certain but I believe milk oolongs are those from the Jinxuan cultivar. It is a relatively new oolong cultivar which are said to have a creamy flavor and texture. Of course I could be mistaken.

I believe these are all correct answers, BUT AFAIK only for the authentic non-scented nai xiang oolong. There are no guarantees when it comes to imitators.

Teaspring.com wrote:Nai Xiang Oolong is a scented tea from Taiwan. The name Nia Xiang means "Milk Fragrant", and as its name suggests, this tea is characterized by a distinct milk-like fragrance and taste. [Emphasis added. Source.]

I am worried by the adjective "scented." Generally speaking, this is another word for "flavored" (yes I know, not exactly, but whatever), so it may contain milk and I would be concerned if you are allergic enough for it to be an issue. It could just be a bad translation/ choice of words on their part, though.

You might try contacting vendors directly. Still, though the vendors would more than likely give honest answers, the tea biz is a shady one so I wouldn't necessarily trust their suppliers.

I admit the wording isn't entirely clear, but I don't think I'm being too alarmist about it. I guess it depends how strong an allergy you have.